Microcystin Contamination Research Articles

Evaluating the potential risk of microcystins to blue crab ( Callinectes sapidus) fisheries and human health in a eutrophic estuary

Toxin producing cyanobacteria commonly inhabit fresh waters and brackish estuaries, and blooms of these species may be escalating worldwide due to eutrophication. The most common cyanobacterial toxins occurring in fresh and brackish waters are microcystins (MC), which are known to accumulate in aquatic organisms. Prey preference for filter-feeding organisms, such as clams and mussels, make the blue crab, Callinectes sapidus, a candidate for microcystin contamination, therefore making this commercially important edible crab species a potential vector of these toxins to humans. The present study was conducted in a hyper-eutrophic freshwater lake, Lac des Allemands, located in the Barataria estuary system of southeastern Louisiana, and was aimed at documenting the presence and abundance of toxic cyanobacteria and assessing microcystin concentrations in surface water and blue crabs taken from this region. Microcystis sp. were the dominant cyanobacteria, with alternating blooms of Microcystis and Anabaena spp. occurring during the 8-month study. Enzyme-linked immunosorbent assay (ELISA) was used to evaluate concentrations of microcystins from surface water and hepatopancreas, viscera, and muscle tissues of blue crabs. The highest concentration of microcystins found in surface water (1.42 μg MC l −1) was above the tolerable daily intake (TDI) guideline for microcystins in drinking water (1.0 μg MC l −1) set by the World Health Organization (WHO). Highest concentration of microcystins occurring in crab tissue were 820 μg MC kg −1 in hepatopancreas, 65 μg MC kg −1 in viscera, and 105 μg MC kg −1 in muscle, which were close to or exceeding the WHO-TDI guidelines for human consumption (0.04 μg MC kg −1 body weight day −1) based on human body weight and amount of crab tissue consumed. This study documents the presence of microcystins in both surface water and blue crab tissue and therefore, demonstrates the potential for Microcystis and Anabaena blooms to produce toxins that may be accumulated in the tissues of blue crabs and transferred to higher level consumers, including humans.

Rapid detection of microcystins in cells and water

Global occurrence and concern about microcystin contamination in water has prompted the development of a range of detection methods for their identification and quantification. However, most protocols are relatively time consuming, expensive and require laboratory expertise. The production of robust and sensitive recombinant antibodies has facilitated the development of a lateral flow immunoassay (ImmunoStrip ®) which can rapidly detect microcystins and nodularins in the field with minimal equipment or processing. Here we evaluate the sensitivity and cross-reactivity of the commercially produced ImmunoStrip ® and apply them to the detection of microcystins in laboratory cultures and natural samples. It was observed that while the ImmunoStrip ® are marketed for the detection of 10 μg/l microcystin, all 7 microcystins and nodularin that were tested were detected below 1 μg/l. Furthermore, microcystins and nodularins were successfully detected in a range of laboratory cultures and samples from irrigation ponds.

Detection of microcystin contamination by the measurement of the variability of the in vivo chlorophyll fluorescence in aquatic plant Lemna gibba

In recent years, chlorophyll fluorescence analysis has become one of the most powerful and widely used techniques available to plant ecophysiologists. In this work, the chlorophyll fluorescence is used in order to evaluate the biotic stress induced by exposure to cyanobacterial toxins (microcystins). Experiments were carried on the aquatic plant Lemna gibba exposed to various concentrations of a microcystins (0.01, 0.03, 0.05, 0.07, 0.15, 0.22 and 0.3 μg equivalent MC-LR.mL −1) during 5 h. The reversibility of the stress changes was also studied following 24 h of treatment. The efficiency and the utility of this biophysical technique were compared to biochemical analysis priory used to evaluate the plant stress induced by such contamination. The results showed that there is a concentration-dependent effect on the measured in vivo chlorophyll fluorescence with significant differences between the control and all concentrations except for 0.01 μg equivalent MC-LR.mL −1. The reversibility tested showed also that after avoiding the contact with the microcystins, the chlorophyll fluorescence measurements were not significantly different from the control. The results showed that if the contact with the microcystins is short and not repeated plants may not suffer from a significant stress. We concluded that this simple and rapid technique based on the variable fluorescence, could be recommended and applied to test the plant stress caused by cyanobacterial toxins.

Hepatotoxicidade associada à microcistina

Urban and industrial discharges, intense agricultural exploitation and fisheries have been causing the eutrophication in both drinking and recreational waters. A frequent consequence of eutrophication in waters is the massive development of cyanobacteria. The occurrence of these blooms induces a severe problem, as Microcystis aeruginosa, the most widespread distributed cyanobacteria, can produce microcystins (MC). Toxic effects of MC have been described in liver, lungs, stomach, and intestine. Deaths in wildlife, livestock and human beings were also associated with MC exposition. MC exposition can occurs directly by ingestion, inhalation, contact, intravenous inoculation of contaminated water (hemodialysis) or indirectly, by the consumption of animals, as fish and mollusks, the majors ingestors of cyanobacteria and its toxins. The most toxic MC, an also the most common is microcystin-LR (MC-LR), that has the liver as the main target organ. Microcystin is taken up specifically into the liver by bile acid transporters and, after entering the cytoplasm, inhibit protein phosphatases 1 and 2A, which leads to the increase in protein phosphorylation. This effect has two main consequences: the destruction of cytoskeleton directly causing cytotoxic effects, and deregulation of cell division, leading to tumor-promoting activity. Acute exposition to MC induces severe intrahepatic hemorrhage, necrosis and apoptosis, while chronic exposure can cause hepatic or intestinal neoplasia. It has been documented that MC hepatotoxicity is closely associated with intracellular reactive oxygen species formation. Natural degradation of microcystins depends on the solar radiation and bacteria. If degradation is insufficient, MC will persist in the freshwater food chain. Microcystin contamination of waters is therefore a hazard to human and animal health, so efforts to avoid eutrophication of waters sources are essential, in order to minimize the risks to public health.

Phytotoxic effects of cyanobacteria extract on the aquatic plant Lemna gibba: Microcystin accumulation, detoxication and oxidative stress induction

The occurrence of toxic cyanobacteria in the aquatic environment constitutes a serious risk for the ecological balance and the functioning of ecosystems. The presence of cyanotoxins in ecosystems could have eventual adverse effects on aquatic plants, which play an important biological role as primary producers. The original aim of this study was to investigate microcystin (MC) accumulation, detoxication and oxidative stress induction in the free-floating aquatic vascular plant Lemna gibba (Duckweed, Lemnaceae). Experiments were carried out with a range of MC levels, obtained from toxic Microcystis culture extracts (0.075, 0.15, 0.22 and 0.3 μg equiv. MC-LR mL −1). During chronic exposure of the plant to MC, we examined the growth, photosynthetic pigment contents and also the physiological behavior related to toxin accumulation, possible biodegradation and stress oxidative processes of L. gibba. For the last reason, changes in peroxidase activity and phenol compound content were determined. This is a first report using phenol compounds as indicators of biotic stress induced by MC contamination in aquatic plants. Following MC exposure, a significant decrease of plant growth and chlorophyll content was observed. Also, it was demonstrated that L. gibba could take up and bio-transform microcystins. A suspected MC degradation metabolite was detected in treated Lemna cells. In response to chronic contamination with MCs, changes in the peroxidase activity and qualitative and quantitative changes in phenolic compounds were observed after 24 h of plant exposure. The physiological effects induced by chronic exposure to microcystins confirm that in aquatic ecosystems plants coexisting with toxic cyanobacterial blooms may suffer an important negative ecological impact. This may represent a sanitary risk due to toxin bioaccumulation and biotransfer through the food chain.

Multiplex PCR for the detection of toxigenic cyanobacteria in dietary supplements produced for human consumption

The production of food supplements containing cyanobacteria is a growing worldwide industry. While there have been several reports of health benefits that can be gained from the consumption of these supplements, there have also been a growing number of studies showing the presence of toxins some of which (for example microcystins) are known to affect human health. In this paper, we report a multiplex polymerase chain reaction (PCR) technique that can be used to identify microcystin contamination in dietary supplements produced for human consumption. This method involves a PCR reaction containing three primer pairs, the first of which is used to amplify a 220-bp fragment of 16s rDNA specific to Microcystis, the most common microcystin-producing cyanobacterium. The second primer pair is used to amplify a 300-bp fragment of the mcyA gene, linked to microcystin biosynthesis in Anabaena, Microcystis, and Planktothrix. A third primer pair, used as a positive control, results in the amplification of a 650-bp fragment from the phycocyanin operon common to all cyanobacteria. This technique was found to be useful for detecting the presence of toxigenic Microcystis in all dietary supplements produced from the nontoxic cyanobacterium Aphanizomenon flos-aquae.

Microcystin diversity in a Planktothrix rubescens population from Lake Albano (Central Italy)

The cyanobacterium Planktothrix rubescens Anagnostidis & Komarek (previously Oscillatoria rubescens DC ex Gomont) is present in several Italian lakes and it is known to produce cyanotoxins. The dynamics and toxin production of P. rubescens population in Lake Albano, a volcanic crater lake in Central Italy, has been studied for 5 years (January 2001–April 2005). Winter–spring superficial blooms with frequent scums were observed every year. Total microcystin (MC) levels were measured from April 2004 to October 2005 by liquid chromatography-tandem mass spectrometry. MC levels up to 14.2 μg/l were measured, with high concentrations found in summer at a 20–25 m depth. The intracellular toxin content varied between 1.5 (surface, January 2004) and 0.21 pg/cell (surface, May 2004). Six different MCs were detected, the most abundant being two desmethyl-MC-RR isomers. Of the 13 water wells monitored in the Lake Albano area, two of them showed MC contamination during winter, confirming the ability of these toxins to migrate through groundwater towards public water sources. These results highlight the need for further studies on the mobility and fate of these pervasive cyanobacterial toxins.

Cyanobacteria and microcystins occurrence in the Guadiana River (SW Spain)

This work reports on the survey carried out to determine the presence of microcystins (MCs) by using ELISA tests and HPLC-UV for such determination in different sample sites along the Spanish course of the Guadiana River. The most important cyanobacteria species identified were, Microcystis aeruginosa and Oscillatoria spp. The highest total microcystin content recorded was 6.40 µg L−1 in 2002. The main toxins found were microcystins RR and LR, with microcystin YR present at trace levels. Improvements in sample clean up were carried out by using Immunoaffinity solid phase extraction (SPE) and its advantages regarding to conventional SPE were clearly demonstrated. The confirmation of MCs presence in the evaluated water reservoirs, underlines the necessity of monitoring programs as well as the improvement of analytical methodologies to efficiently prevent the human health risks as a consequence of MCs contamination.

Degradation of microcystin toxins in a falling film photocatalytic reactor with immobilized titanium dioxide catalyst

The increasing incidence of algal blooms in fresh water supplies and the consequent possibility of cyanobacterial microcystin contamination of potable water is a cause of recent concern. Heterogeneous photocatalytic oxidation forms part of a family of advanced water treatment technologies comprising the generation of reactive oxidizing species in water media and results in the complete oxidative degradation (mineralization) of organic pollutants to yield carbon dioxide, water and inorganic ions. A new experimental laboratory-scale ‘falling film’ reactor has been developed to study the photocatalytic degradation of microcystins in aqueous solution. The reactor consisted of a fiberglass sheet impregnated with immobilized titanium dioxide (TiO 2) catalyst over which the microcystin solution was pumped (as a falling film) while being irradiated from UV-C germicidal lamps. The design of the system obviated the necessity to separate suspended catalyst from treated water as required in slurry reactors. The photocatalytic degradation was characterized by pseudo-first order reaction kinetics. Rapid degradation of microcystins LR, YR and RR was observed in natural lake water with half lives less than 10 min, while even faster rates were achieved in laboratory distilled water. Although low pH (pH 3) marginally improved reaction rates, the presence of radical scavengers such as sulfate ions was detrimental to the photocatalytic oxidation process.

Ingestion of toxic Microcystis aeruginosa by dairy cattle and the implications for microcystin contamination of milk

Microcystin (MCYST) toxins can be produced by the bloom-forming cyanobacterium Microcystis aeruginosa. They are chemically stable compounds and have both acute and chronic effects on the health of mammals, including cattle and humans. Cattle will drink water containing lethal cell concentrations of M. aeruginosa. When cattle consume sub-lethal doses of microcystins, the fate of those toxins is unknown. We provided drinking water containing 1×10 5 cells ml −1 M. aeruginosa (strain MASH01-A19) to four lactating Holstein–Friesian dairy cattle for 21 days to determine if MCYST-LR produced by the cyanobacteria, could be detected in milk produced by the cattle. Cattle consumed up to 15 mg MCYST-LR at an ingestion rate of 1.21 μg kg (live weight) d −1. Analysis by HPLC and ELISA indicated that no detectable amounts of microcystin from the cyanobacteria were present in the milk obtained from the treated animals. Based on the level of quantitation of the ELISA analyses, the maximum possible concentration in the milk was less than 2 ng l −1. This is more than three orders of magnitude less that the concentration that could be considered problematic for milk of 0.86 μg l −1 which we calculated using the World Health Organization derived tolerable daily intake for MCYST-LR and the per capita daily consumption of milk in Australia.

Microcystin contamination in fish from the Jacarepaguá Lagoon (Rio de Janeiro, Brazil): ecological implication and human health risk

Chronic and subchronic toxicity from exposure to microcystins, cyclic peptide liver toxins from certain cyanobacteria, poses an important hazard, which has received little study. No in vivo information exists on accumulation and transfer of microcystin from the food chain to humans. This paper present results of a 3-year study that demonstrates bioaccumulation of microcystins by fish and potential rates of microcystin ingestion by humans. The study was carried out in a shallow coastal lagoon in the city of Rio de Janeiro (Jacarepaguá Lagoon). Fish (Tilapia rendalli) were collected every 2 weeks from August 1996 to November 1999. Microcystins were analyzed by HPLC in phytoplankton, fish liver and viscera while fish muscle tissue was analyzed by enzyme linked immunosorbant assay (ELISA). Phytoplankton samples, dominated by the genus Microcystis, were confirmed to contain microcystins as were fish livers, viscera and muscle tissue. During the entire study period, including times of low water bloom densities, fish muscle tissue contained concentrations of microcystins close to or above the recommended limit for human consumption (0.04μgkg−1 day). Our findings demonstrate that microcystins can accumulate in fish tissue used for human consumption. Rates of ingestion routinely exceed the TDI guidelines as set by the WHO for drinking water. Appropriate epidemiology and risk assessment should be undertaken so that an acceptable TDI and appropriate risk management decisions can be made for human consumption of fish which are harvested from cyanobacterial blooms that contain cyanotoxins.

Assessing potential health risks from microcystin toxins in blue-green algae dietary supplements.

The presence of blue-green algae (BGA) toxins in surface waters used for drinking water sources and recreation is receiving increasing attention around the world as a public health concern. However, potential risks from exposure to these toxins in contaminated health food products that contain BGA have been largely ignored. BGA products are commonly consumed in the United States, Canada, and Europe for their putative beneficial effects, including increased energy and elevated mood. Many of these products contain Aphanizomenon flos-aquae, a BGA that is harvested from Upper Klamath Lake (UKL) in southern Oregon, where the growth of a toxic BGA, Microcystis aeruginosa, is a regular occurrence. M. aeruginosa produces compounds called microcystins, which are potent hepatotoxins and probable tumor promoters. Because M. aeruginosa coexists with A. flos-aquae, it can be collected inadvertently during the harvesting process, resulting in microcystin contamination of BGA products. In fall 1996, the Oregon Health Division learned that UKL was experiencing an extensive M. aeruginosa bloom, and an advisory was issued recommending against water contact. The advisory prompted calls from consumers of BGA products, who expressed concern about possible contamination of these products with microcystins. In response, the Oregon Health Division and the Oregon Department of Agriculture established a regulatory limit of 1 microg/g for microcystins in BGA-containing products and tested BGA products for the presence of microcystins. Microcystins were detected in 85 of 87 samples tested, with 63 samples (72%) containing concentrations > 1 microg/g. HPLC and ELISA tentatively identified microcystin-LR, the most toxic microcystin variant, as the predominant congener.

Assessing Potential Health Risks from Microcystin Toxins in Blue-Green Algae Dietary Supplements

The presence of blue-green algae (BGA) toxins in surface waters used for drinking water sources and recreation is receiving increasing attention around the world as a public health concern. However, potential risks from exposure to these toxins in contaminated health food products that contain BGA have been largely ignored. BGA products are commonly consumed in the United States, Canada, and Europe for their putative beneficial effects, including increased energy and elevated mood. Many of these products contain Aphanizomenon flos-aquae, a BGA that is harvested from Upper Klamath Lake (UKL) in southern Oregon, where the growth of a toxic BGA, Microcystis aeruginosa, is a regular occurrence. M. aeruginosa produces compounds called microcystins, which are potent hepatotoxins and probable tumor promoters. Because M. aeruginosa coexists with A. flos-aquae, it can be collected inadvertently during the harvesting process, resulting in microcystin contamination of BGA products. In fall 1996, the Oregon Health Division learned that UKL was experiencing an extensive M. aeruginosa bloom, and an advisory was issued recommending against water contact. The advisory prompted calls from consumers of BGA products, who expressed concern about possible contamination of these products with microcystins. In response, the Oregon Health Division and the Oregon Department of Agriculture established a regulatory limit of 1 microg/g for microcystins in BGA-containing products and tested BGA products for the presence of microcystins. Microcystins were detected in 85 of 87 samples tested, with 63 samples (72%) containing concentrations > 1 microg/g. HPLC and ELISA tentatively identified microcystin-LR, the most toxic microcystin variant, as the predominant congener.

Survey of microcystins in water between 1995 and 1996 in Paraná, Brazil using ELISA.

An enzyme-linked immunosorbent assay (ELISA) based on a monoclonal antibody was used to determine microcystin (MC) concentrations in water supplies and water plant samples collected between November 1995 and October 1996, from five regions of Paraná, Brazil. In addition, the presence of Microcystis sp. was monitored. Of the 50 samples obtained, 12 were from an urban lake, 8 from human water supplies, 10 from recreational lakes, 13 from farm waters used for animal pasture and 7 from aquaculture facilities. M. aeruginosa was positive in all locations. MCs were positive (>50 pg ml(-1)) in 9 samples (2 samples from human water supplies, 5 from recreational lakes and 2 from animal pasture). Heavy contamination with MCs was observed in water samples collected in May 1996 from 2 recreation (swimming-fishing sites at Itaipu dam, 6380 and 10,000 pg ml(-1)) and human supplies (6627 pg ml(-1)) samples. At these sites, a large bloom of Microcystis sp. was detected. Treatment with 1 ppm Cl- reduced MCs levels, although 267 pg ml(-1) remained in the water plant samples. Our data showed frequent occurrence of Microcystis sp., which may be a hazard to humans and animals in the state of Paraná. More detailed investigations are required to evaluate the risk of natural MC contamination in the water supplied in this region.

Survey of Microcystins in water between 1995 and 1996 in Paraná, Brazil using ELISA

An enzyme-linked immunosorbent assay (ELISA) based on a monoclonal antibody was used to determine microcystin (MC) concentrations in water supplies and water plant samples collected between November 1995 and October 1996, from five regions of Paraná, Brazil. In addition, the presence of Microcystis sp. was monitored. Of the 50 samples obtained, 12 were from an urban lake, 8 from human water supplies, 10 from recreational lakes, 13 from farm waters used for animal pasture and 7 from aquaculture facilities. M. aeruginosa was positive in all locations. MCs were positive (>50 pg ml−1) in 9 samples (2 samples from human water supplies, 5 from recreational lakes and 2 from animal pasture). Heavy contamination with MCs was observed in water samples collected in May 1996 from 2 recreation (swimming–fishing sites at Itaipu dam, 6380 and 10 000 pg ml−1) and human supplies (6627 pg ml−1) samples. At these sites, a large bloom of Microcystis sp. was detected. Treatment with 1 ppm Cl− reduced MCs levels, although 267 pg ml−1 remained in the water plant samples. Our data showed frequent occurrence of Microcystis sp., which may be a hazard to humans and animals in the state of Paraná. More detailed investigations are required to evaluate the risk of natural MC contamination in the water supplied in this region. Copyright © 1999 John Wiley & Sons, Ltd.

Photocatalytic degradation of cyanobacterial microcystin toxins in water

The microcystins are hepatotoxins produced by a number of cyanobacterial species (blue–green algae) in fresh water systems. The increasing eutrophication of natural waters has led to an increase in the incidence of algal blooms and the consequent increased risk of microcystin contamination of water resources. The removal of microcystins LR, YR and YA from contaminated water was investigated using an experimental laboratory-scale photocatalytic `falling film' reactor in which an oxygen purge, UV radiation and semiconductor titanium dioxide (TiO 2) catalyst were used to oxidatively decompose the microcystin pollutants. Preliminary studies, using algal extracts spiked into distilled water, indicated that the microcystins were rapidly decomposed in this reactor. The decomposition followed first order reaction kinetics with half-lives of less than 5 min with the reactor operating in a closed-loop mode. Reaction rates were strongly dependent on the amount of TiO 2 catalyst (0–5 g/l), but only marginally influenced by a change in gas purge from oxygen to compressed air. The use of lake water, rather than distilled water, showed that this process is feasible in natural waters, although increased levels of catalyst (up to 5 g/l) were required to achieve comparable decomposition rates.